1. Field of the Invention
This invention relates to an endoscope system that is equipped with a video-scope and a video-processor, and particularly to enlarging an image that is obtained by the image sensor.
2. Description of the Related Art
A video-scope (electronic endoscope) is equipped with an image sensor. Since the size of the image sensor is restricted because of the thinness of the tip portion, the number of pixels in the image sensor is generally smaller than that of a monitor that displays an observed image. Therefore, an interpolation process is carried out to enlarge the size of an image obtained by the image sensor. Usually, one field's or frame's worth of image data is temporarily stored in a field/frame memory, and an interpolation process is carried out for the stored image data. However, an interpolation process with a field/frame memory increases electric power consumption and the amount of data to be transferred and processed, thereby decreasing a performance of a system.
To avoid reduced performance, an interpolation process that utilizes line memories is carried out. JP1989-261086A discloses the lower-order (e.g., the second order) interpolation process, in which an interpolation line is added by using two neighboring lines' worth of pixel data that are stored in line memories. JP2000-184295A discloses the simple interpolation process that adds an interpolation line by using a neighboring line directly.
The lower-order interpolation process or simple interpolation process using a line memory(s) cannot generate an enlarged image with high resolution. Recently, displaying an observed image with high quality is required to accurately diagnose certain medical problems. The above interpolation processes cannot sufficiently achieve the high quality required of an observed image in the endoscope field.